A solar photovoltaic installation is a system. Each subsystem has a precise role and its own safety requirements. This guide develops the indispensable components, their sizing, the mandatory protections and best practices to achieve performance, safety and durability.
Useful references to deepen each topic: the article on IP protection, the category of enclosures, families of waterproof boxes and IP68 junction boxes, the industrial range Indubox IP65, and complementary content on IK protection, overvoltages, short circuits and fuses.
Quick summary
| Element | Main function | Key protections | Watch points |
|---|---|---|---|
| PV modules | Convert solar irradiance into DC power | SPD type 2 DC, earthing, PV cable H1Z2Z2-K | Orientation, shading, string voltage within MPPT window |
| Charge controller (battery-DC systems) | Optimise and protect battery charging | gPV fuses, DC isolator, SPD type 2 | MPPT vs PWM, V/I compatibility and charge profile |
| Batteries | Store energy for deferred use | BMS, DC fuses, ventilation as per chemistry | Depth of discharge, cycles, temperature |
| Inverter | Convert DC to AC for the internal installation | SPD type 2 AC, RCD, MCB | DC/AC sizing, anti-islanding, efficiency |
| DC/AC protection boards | Safety of people and assets | DC isolator, gPV fuses, SPD, RCD/MCB | Proper IP rating, labelling, selectivity |
1) PV modules / Solar panels
PV modules are the collector surface. They are arranged in strings (series connection) that must deliver a voltage compatible with the inverter’s MPPT window and a current consistent with cable sections and protections.
Basic sizing: define target peak power, number of modules per string and guarantee that open-circuit voltage stays within inverter limits at temperature extremes. Manage shading, orientation and tilt for seasonal yield. A slight DC oversizing versus inverter AC power often improves behaviour in low irradiance.
Cabling and protections: PV cable H1Z2Z2-K, compatible connectors (MC4-type), DC SPD at the generator and earthing of structures. House these devices in enclosures with suitable IP rating. See enclosures and waterproof boxes.
2) Charge controller
Used in autonomous or hybrid systems with battery on the DC side, the charge controller manages charging quality and protects storage. MPPT controllers maximise the operating point under variable irradiance and temperature. PWM devices are simpler but less efficient.
Checks: V/I compatibility with the PV array, charge curve for the selected chemistry, thermal dissipation and environmental conditions. Integrate DC isolator, gPV fuses and DC SPD inside an enclosure with appropriate IP. Explore options in Solera enclosures.
3) Batteries
Batteries enable consumption beyond sun hours. Main families: lead-acid (AGM, gel) and lithium (LiFePO4), with lithium offering higher energy density and cycle life plus an integrated BMS.
Quick sizing: capacity (kWh) ≈ daily consumption × days of autonomy ÷ admissible depth of discharge. Consider peak power and ambient temperature. Install in a ventilated enclosure and protect the DC circuit with fuses, isolator and SPD. For selection of sealed boxes and higher-end lines like Vera waterproof distribution boxes, consult the catalogue.
4) Solar inverter
The inverter converts DC to AC. Main architectures: string/central inverters, micro-inverters and systems with power optimisers at module level.
- String/central: industry standard, centralised maintenance.
- Micro-inverters: useful with partial shading; module-level monitoring.
- Optimisers: compromise between module control and central management.
Selection and protections: verify MPPT window, VDC max, input current, European efficiency and grid requirements. On AC: MCB, appropriate RCD and AC SPD. House protections in enclosures with the right IP rating for indoor or outdoor use. Example families: Indubox IP65 and mounted sealed boxes.
5) DC and AC protection boards
The protection board integrates devices that protect people and the installation. In PV, it is common to separate a DC board (generator side) and an AC board (inverter / internal network).
5.1 DC board: typical protections
- DC isolator with load-break capability.
- gPV fuses per string or pole depending on architecture.
- DC SPD (usually type 2) sized to system voltage.
- Earth bars and clear polarity labelling.
Install all inside an enclosure with suitable IP rating for weather and UV. See waterproof boxes or IP68 junction boxes for exposed areas.
5.2 AC board: typical protections
- MCB matched to inverter nominal current.
- RCD (type and sensitivity per inverter and installation).
- AC SPD (type 2) near the inverter and coordinated with the main board.
Select enclosures and accessories consistent with the environment. Compare options in Solera enclosures and review IP selection criteria.
6) Cabling, connectivity and earthing
Use certified PV cables for outdoor service, compatible connectors correctly crimped, glands with reliable sealing, and a robust equipotential earthing scheme.
- Sections: size for voltage drop and heating.
- Routing: minimise loop areas, avoid sharp edges and protect against UV.
- Labelling: clear identification of strings, polarities and protections.
For sealed interfaces and submerged or wet zones, see IP68 junction boxes and complementary IP68 connectors.
7) Monitoring, maintenance and safety
Monitoring via the inverter or dedicated gateways helps analyse production, detect drifts and plan maintenance. Implement a preventive maintenance programme: visual inspection of cables and enclosures, RCD tests, torque checks and continuity of earths, connector inspection. Practical guidance here: Preventive maintenance in electrical installations.
During works: lockable isolators, clear safety signage and appropriate PPE. After commissioning: a technical dossier with single-line diagram, data sheets for protections and labelling in boards. Consult related topics on overvoltages and IK resistance.
8) Step-by-step sizing: practical method
- Load and profile: estimate daily consumption and peak power.
- Generator: choose modules and modules per string according to MPPT window.
- Inverter: select AC power, MPPT inputs, efficiency and protections.
- Storage (if applicable): capacity in kWh, max current, BMS and ventilation.
- Protections: define DC/AC boards, SPDs, gPV fuses and RCDs/MCBs.
- Enclosures: select IP per environment; see enclosure families and Indubox IP65.
- Validation: check voltage drops, heating, selectivity and labelling.
9) Common mistakes to avoid
- Under/oversizing string voltage versus the MPPT window.
- Forgetting SPD coordination between DC and AC boards.
- Neglecting the IP rating against rain, dust or UV.
- Mixing incompatible connectors from different brands.
- Lack of labelling and documentation inside the board.
Frequently asked questions
How many modules for 1 kWp?
It depends on the module’s rated power. Most residential roofs use modules of several hundred watts-peak. Calculate the total number to reach the target and keep within the inverter’s admissible DC voltage.
Are batteries always necessary?
No. They are essential in off-grid sites or when you aim to raise self-consumption. Without storage, production is consumed in real time.
Which IP should I choose for the boards?
It depends on location. Outdoors, choose a higher IP. See selection criteria in IP protection and browse waterproof boxes or IP68 junction boxes.
Related resources
- 5 key elements in a PV installation
- Enclosures and boards
- IP68 connection boxes
- Indubox industrial IP65
- Brochures and catalogues (PDF)
Conclusion
The five essential elements of a photovoltaic installation are: modules, charge controller (if there is DC storage), batteries (depending on the goal), inverter and DC/AC protection boards. Their sizing and protection coordination determine overall efficiency and safety. To select enclosures by environment, rely on the IP guide, explore enclosure families and consult current brochures.